How to bleed your radiators

When air builds up inside a radiator, it can stop it working to its full capacity, meaning a colder house and higher heating bills.

Learn how to tell if your radiators need bleeding and how to bleed your radiators with our handy guide.

Thinking about your heating costs this winter? Head to our tips for reducing your heating bills 

How do I know if my radiators need bleeding?

Radiators need bleeding every few years to get rid of trapped air bubbles.

These air bubbles rise to the top of a radiator when it's on, so place your hand on the top while the heating is on. If the top of the radiator is cool, or much colder than the bottom of the radiator, it's a sign your radiators need bleeding. 

Bleeding your radiators is usually a simple job and can quickly fix a radiator that's too cold. But if your whole house feels as though it's not heating up correctly, you might have an unbalanced heating system. This is a bigger issue to fix, and will need a plumber or heating engineer. 

Find out more about how to diagnose an unbalanced system and what to do about it in our guide to balancing your radiators.

How to bleed your radiators

Bleeding a radiator is a task you can carry out yourself. All you need is your radiator bleed key, and a spare cloth or towel. You'll also need a container to catch any water that comes out of your radiator when you start bleeding it.

1. Turn the heating off Let the radiator cool down for 20-30 minutes so you don't risk burning yourself with hot water. 
2. Locate the radiator's bleed valve Usually located on the side of the radiator, at its top. If you're bleeding multiple radiators, start with the one on the ground floor furthest from your boiler.
3. Place a container under the valve This is to catch any water that may drip out of the valve. Also hold the spare cloth or towel under the valve.
4. Insert the radiator bleed key and open the valve slowly, turning anticlockwise, until you hear a hissing sound. This is the trapped air escaping. Only open the valve a maximum of half-a-turn, so any water doesn't escape too quickly.
5. Close the valve when water starts leaking out At this point all the trapped air has been removed, so turn the key clockwise to close it. Repeat for all the radiators you need to bleed.
6. Check your boiler's pressure After bleeding several radiators, it is normal for the heating system's pressure to drop. Check the boiler's pressure indicator, which should be between 1.0 and 2.0 bar (often highlighted green).
7. Increase the boiler pressure if needed - follow the manufacturer's instructions to do this. Our guide to dealing with common boiler problems also explains what to do. If you’re unsure contact your boiler manufacturer or a qualified heating engineer.
8. Turn the heating on Give your radiators time to heat up and check the cold areas at the top of the bled radiators have gone. 

Read our guide on getting the best boiler service to get your boiler running as efficiently as possible